Russian-backed leaders in four regions of Ukraine are to hold so-called referendums on joining Russia in the coming days.
Here are the latest developments:
- Self-styled referendums on joining Russia are to be held in Kherson, Zaporizhzhia, Donetsk and Luhansk between 23 and 27 September
- Russian President Vladimir Putin has ordered a partial mobilisation of about 300,000 reservists to reinforce his troops in Ukraine
- Ukrainian forces have held ground taken from Russia earlier this month in Kharkiv
- Ukrainian troops are trying to push forward around Lyman
- Fighting continues in the south, around Kherson
So-called referendums in four regions
Four regions of Ukraine that are partially or almost completely occupied by Russia will hold self-styled referendums from 23 to 27 September.
Voting in Kherson, Zaporizhzhia, Donetsk and Luhansk will be conducted either in person or remotely.
The Russian-installed head of Kherson region in the south, Vladimir Saldo said incorporating it into Russia would "secure our territory and restore historical justice".
Large parts Zaporizhzhia and Donetsk are not under Russian control and all four regions have seen fighting in recent days, so conducting a secure vote will not be possible.
Russian President Vladimir Putin is expected to annex the four regions in the days following the referendums.
Some analysts have suggested that the change will allow Russia to claim that continued Ukrainian counter-attacks on the four regions will be an attack on sovereign Russian territory.
On Wednesday, Mr Putin ordered a partial mobilisation of about 300,000 Russian reservists, stressing that the call up would apply to people who already have military training.
Russia's defence minister, Sergei Shoigu, said that the extra troops were required to defend a front line stretching for some 1,000km (600 miles).
Russian retreat in the east
The announcements of the partial mobilisation and the referendums came after a major Russian defeat in the east.
Ukraine says it recaptured 6,000 sq km (2,317 sq miles) of territory from Russia earlier this month, when it forced Russian units back in the Kharkiv region.
Russian troops withdrew from the key towns of Izyum and Kupiansk, saying that the retreat would allow its troops to "regroup".
Both towns were major logistical hubs for Russian forces in Donbas.
On Wednesday, Russian units continued to shell central areas of Kupiansk.
Justin Bronk of the Royal United Services Institute (Rusi) told the BBC that Russian positions in Kharkiv had suffered a "total collapse."
The Russian withdrawal was, he said, "certainly the most dramatic reverse that we've seen from the Russians since they retreated from Kyiv in April".
Mr Putin has said that Russian forces were fighting for the "liberation" of the Donbas, which broadly refers to Ukraine's eastern regions of Donetsk and Luhansk, where Russian-backed separatists held significant territory before the invasion.
On Monday, Russia lost full control of Luhansk after a village close to Lysychansk was recaptured by Ukrainian troops.
Reports suggest that Ukrainian units are attempting to push forward in Lyman.
Ukrainian counter-attack continues in the south
Ukraine has continued to attack Russian positions near Kherson, targeting Russian transportation and logistics facilities.
Reports suggest Ukrainian troops have made gains at several locations on the Russian front line in recent weeks.
They have also attacked bridges, ferries and pontoons, attempting to make Russian positions of the west side of the Dnieper River unsustainable, and thereby force a withdrawal.
Also in the south, the International Atomic Energy Agency (IAEA) has called for the demilitarisation of the Zaporizhzhia nuclear power plant.
Russian and Ukrainian sources have accused each other of shelling close to the plant, which is Europe's biggest nuclear facility.
Shelling continued on Wednesday, damaging one of the plant's power units.
Russia's military took over the power station in early March, but it is still being operated by Ukrainian staff.
Western weapons boost Ukraine
Ukrainian President Volodymyr Zelensky has appealed for more funding and equipment to retain the areas retaken from Russia.
Western shipments of weaponry are being used heavily by Ukrainian forces.
Early in the conflict Ukraine used primarily Warsaw Pact munitions, which they had been using for several decades.
But many units have now made the transition to Nato standard equipment, including artillery and ammunition.
Multiple launch rocket systems such as the US-made Himars have been used in both Kharkiv and Kherson, according to the ISW.
Mr Zelensky says: "Our main goal is to de-occupy our whole territory."
Russia invaded Ukraine on 24 February, but Ukrainian forces retook large areas around Kyiv in early April after Russia abandoned its push towards the capital.
Areas in the west of the country, including Lviv, have seen missile attacks but no attempt by Russian forces to take and occupy ground.
The Russians have suffered heavy losses since the invasion began and significant quantities of Russian weaponry have also been destroyed or captured.
By David Brown, Bella Hurrell, Dominic Bailey, Mike Hills, Lucy Rodgers, Paul Sargeant, Alison Trowsdale, Tural Ahmedzade, Mark Bryson, Zoe Bartholomew, Sean Willmott, Sana Dionysiou, Joy Roxas, Gerry Fletcher, Jana Tauschinsk, Debie Loizou, Simon Martin and Prina Shah.
About these maps
To indicate which parts of Ukraine are under control by Russian troops we are using daily assessments published by the Institute for the Study of War with the American Enterprise Institute's Critical Threats Project.
To show key areas where advances are taking place we are also using daily updates from the UK Ministry of Defence and BBC research.
The situation in Ukraine is fast moving and it is likely there will be times when there have been changes not reflected in the maps.